#include<stdio.h>
int fun(int x)
{
	if (x <= 2)
		return 1;
	else
		return fun(x - 2) + fun(x - 1);
}
int main()
{
	int num;
	scanf_s("%d", &num);
	int sum;
	sum=fun(num);
	printf("%d", sum);
	return 0;
}